The technical field relates generally to NOx control in internal combustion engines, and more particularly relates to NOx control in reciprocating piston engines with common rail fuel injection. Modern internal combustion engines must meet stringent emissions standards, including a maximum amount of nitrogen oxides (NOx) that may be emitted. Many engines now utilize aftertreatment systems to reduce engine-out emissions to regulatory levels before release to the atmosphere. The process of regenerating the aftertreatment systems often introduces an increased emissions burden on the system, especially when regenerating certain types of aftertreatment components such as a diesel particulate filter (DPF) or NOx adsorber. Any increase of emissions during a regeneration event must be accounted for in the total emissions of the engine. Accordingly, there is a demand for further improvements in this area of technology.